This study explores the astronomical misconceptions of 10 South African science teachers, focusing on core concepts like earth’s rotation, tilt, eclipses, seasonal shifts, day-night cycles, and planetary revolution. In-depth case studies reveal significant gaps in teachers’ subject matter knowledge and pedagogical content knowledge, affecting their instructional delivery. The findings show teachers struggle with abstract concepts, often using informal language and lacking scientific precision. Many demonstrated incomplete or inaccurate understanding, highlighting the need for targeted professional development to boost conceptual mastery and instructional confidence. Limited teacher knowledge can hinder learners’ opportunities to develop accurate scientific understandings, emphasizing the importance of ongoing support. This research contributes to the growing evidence on the critical role of teacher knowledge in science education, particularly in complex topics like astronomy. The study’s findings have implications for teacher education, professional development, and science curriculum design, underscoring the need for sustained investment in teacher support. The research highlights the importance of addressing teacher knowledge gaps to improve science education in South Africa.